Survival of microorganisms in laundered polyester-cotton sheeting

The effects of wash-water temperature, cold-water or regular detergent, wash-cycle design, drying, and drying temperature on survival of four microorganisms on polyester-cotton sheeting were examined. Escherichia coli T3 bacteriophage survived washing at 24, 35, 46, and 57 C, but not at 68 C. Serratia marcescens survived only the lowest three wash temperatures. Levels of residual Staphylococcus aureus were diminished at the highest two wash temperatures, but survival was substantial even at 68 C. Counts of Bacillus stearothermophilus spores were not altered appreciably by wash temperature. Type of detergent had no practical effect on observed counts. The regular wash cycle was significantly more efficient in removal of microorganisms than the permanent-press cycle. Counts, especially of the bacteriophage and the gramnegative bacterium, were decreased by drying; after drying, the effects of wash-water temperature on S. aureus and B. stearothermophilus were not significantly different. Microorganisms were transferred from inoculated to sterilized sheeting during laundering. The public health significance of these observations is discussed.